The invention relates to a method of pressure bonding a bumped electronic part and an apparatus for pressure bonding a bumped electronic part.
A bumped electronic part has a number of bumps on the lower face. Such a part can be correctly mounted on a substrate by uniformly pressure bonding all the bumps to electrodes of a circuit pattern of the substrate.
Generally, bumps of a bumped electronic part have different heights. When a substrate which is soft and easily flexible is used, the difference in height of the bumps may be absorbed by adjusting the degree of flexure of the substrate. However, substrates include those which are hard or only partially flexible, such as a glass epoxy substrate. When such a substrate is used, the difference in height of the bumps cannot be absorbed by adjusting the degree of flexure of the substrate.
In order to correctly mount a bumped electronic part as described above, all the bumps must be pressure bonded to electrodes of a substrate while the bumps are pressed against the electrodes by a uniform force. In an actual process, however, the difference in height of the bumps, when there is parallelism between the lower face of a suction tool for pressure bonding and the upper face of the substrate, causes a force to be concentrically applied only to a part of the bumps, so that nonuniform pressure bonding easily occurs. A method is known in which, in order to suppress nonuniform pressure bonding, a pressure bonding head has a tilting mechanism using a spherical bearing and the lower face (more correctly, the arrangement plane of bumps) of the suction tool imitates the upper face of the substrate.
The pressure bonding method of the prior art which uses a pressure bonding head has a problem in that, when a substrate and a bumped electronic part are to be positioned while the bumped electronic part is held by the suction tool, the suction tool swings because of the tilting mechanism, whereby the relative positions between electrodes of the substrate and the bumps are disordered.
The method has a further problem in that, when the bumped electronic part is to be bonded to the substrate while the bumped electronic part is held by the suction tool, the suction tool is rotated by the tilting mechanism in a direction (.theta. direction) about a Z-axis which is perpendicular to the substrate, whereby the relative positions between electrodes of the substrate and the bumps are disordered. When a flip chip in which bumps are formed on electrodes of a semiconductor IC is to be mounted on a substrate, particularly, the mounting must be conducted with high accuracy, and hence the problem is noticeable.